Method of making polypyrrole and silver vanadium oxide composite

ABSTRACT

In one embodiment of the present disclosure, a composite electrode for a battery is provided. The composite electrode includes silver vanadium oxide present in an amount from about 75 weight percent to about 99 weight percent and polypyrrole present in an amount from about 1 weight percent to about 25 weight percent.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims priority to U.S.Provisional Application Ser. No. 60/727,686 having a filing date of Oct.17, 2005, and U.S. Provisional Application Ser. No. 60/760,847 having afiling date of Jan. 20, 2006.

BACKGROUND

Silver vanadium oxide (SVO), Ag₂V₄O₁₁, shows high gravimetric andvolumetric energy densities. When SVO is used as a positive electrode inbatteries in implantable medical devices, it performs most of the timeat low power and occasionally delivers one or more high power pulses.SVO provides an electrode potential curve with multiple plateaus, whichallows one to accurately predict the lifetime of the battery.

The synthesis methods of SVO are divided broadly into twocategories—decomposition and combination reaction methods. The formermethod uses decomposable silver compounds accompanied by the evolutionof toxic NO_(x) gas during heat-treatment. In the combination reactionmethod, silver oxide Ag₂O reacts at high temperature with vanadiumpentoxide V₂O₅ in 1:2 molar ratio without liberating any gaseousproducts. The combination reaction leads to a well-crystallized SVO withhigher surface area, when compared with the material synthesized usingthe decomposition reaction.

While the theoretical discharge capacity characteristics of SVO arequite high, much lower utilization of SVO is typically attained,especially at high discharge rates due to high particle-to-particleresistance and electrical resistivity of SVO. The internal cellresistance increases with progressing discharge, resulting in a poorpower capability in Lithium/SVO cells. While attempts have been made toimprove the electrochemical performance of the SVO electrodes byoptimizing the synthesis process and by introduction of substitutionatoms, a need exists enhanced discharge capacity and rate capability.

SUMMARY

The present disclosure recognizes and addresses the foregoing needs aswell as others. Objects and advantages of the invention will be setforth in part in the following description, or may be obvious from thedescription, or may be learned through the practice of the invention. Inone embodiment of the present disclosure, a composite electrode for abattery is provided. The composite electrode includes silver vanadiumoxide present in an amount from about 75 weight percent to about 99weight percent and polypyrrole present in an amount from about 1 weightpercent to about 25 weight percent.

In certain embodiments, the polypyrrole may be present in an amount fromabout 5 weight percent to about 15 weight percent. In some embodiments,the polypyrrole may be present in an amount from about 7 weight percentto about 12 weight percent. In certain embodiments, said electrode maybe located in a lithium battery. In such embodiments, the battery mayhave a discharge capacity from about 255 mAh g-1 to about 315 mAh g-1.In certain embodiments, the battery may have a discharge capacity fromabout 275 mAh g-1 to about 310 mAh g-1. In certain embodiments, thebattery may have a discharge capacity from about 285 mAh g-1 to about305 mAh g-1. In some embodiments, the electrode may include the cathodeof the battery. In certain embodiements, the battery may be used in amedical device. In some embodiments, the electrode may include carbon.

In another embodiment of the present disclosure, a process for synthesisby oxidative polymerization is provided. The process includes contactingsilver vanadium oxide with an acidic solution to form a solutioncontaining silver vanadium oxide and contacting pyrrole with thesolution containing silver vanadium oxide to form a composite materialincluding polypyrrole and silver vanadium oxide.

Other features and aspects of the present disclosure are discussed ingreater detail below.

DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure, including the best mode thereof to oneof ordinary skill in the art, is set forth more particularly in theremainder of the specification, including reference to the accompanyingfigures in which:

FIG. 1 illustrates XRD patterns of (a) SVO(N), (b) SVO(A) and (c)PPy/SVO(A) powder specimens, with the arrows in FIG. 1( a) representingthe peaks due to the Ag_(1.2)V₃O₈ phase;

FIG. 2 illustrates FT-IR spectra measured on the KBr-diluted pellets of(a) SVO(A) and (b) PPy/SVO(A);

FIG. 3 illustrates plots of the PPy and SVO(A) contents in the compositeelectrode against the liquid pyrrole concentration in the polymerizationbath determined by TGA;

FIG. 4 illustrates (a) Galvanostatic discharge curves at the rate ofC/25 and (b) specific discharge capacities as a function of thedischarge rate, obtained for SVO(N), SVO(A) and 7 wt % PPy/SVO(A), withthe specific discharge capacity calculated based on the weight of activematerial;

FIG. 5 illustrates (a) theoretical and experimental discharge capacitiesof PPy/SVO(A) and (b) utilization of SVO(A) in PPy/SVO(A) as a functionof the PPy content, with the full utilization of PPy assumed with acapacity of 72 mAh g⁻¹;

FIG. 6 illustrates typical current responses of 7 wt % PPy/SVO(A) todifferent potential steps;

FIG. 7 illustrates Nyquist plots of the ac-impedance spectrum for 7 wt %PPy/SVO(A) at different electrode potentials: (a) 3.4 V vs. Li/Li⁺, (b)2.8 V vs. Li/Li⁺ and (c) 2.0 V vs. Li/Li⁺;

FIG. 8 illustrates plots of the charge transfer resistance against theelectrode potential, obtained for SVO(A) and 7 wt % PPy/SVO(A); and

FIG. 9 illustrates plots of the chemical diffusivity of lithium inSVO(A) and 7 wt % PPy/SVO(A) with respect to the electrode potential.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentdisclosure, which broader aspects are embodied in the exemplaryconstruction.

The present disclosure is generally directed to a composite electrodeand a process for making the same. In accordance with certain aspects ofthe present disclosure, a novel process of synthesizing a polypyrrole(PPy) and silver vanadium oxide (SVO) composite material is described.Such a process allows for an increase in the discharge capacity andimprovement in the rate capability of an SVO electrode. The PPy/SVOcomposite electrodes are prepared by an oxidative polymerization ofpyrrole monomer on the SVO surface in acidic solution.

Typically, the discharge capacity of a Li/SVO cell is much lower thanthe theoretical value, especially at high discharge rates, due to highparticle-to-particle resistance and electrical resistivity of SVO. SincePPy possesses its own capacity to intercalate ions, and also promotesinsertion into SVO, the PPy/SVO composite electrode yields higherdischarge capacity than a pristine SVO electrode. Furthermore, PPy has ahigh electrical conductivity, so it greatly reduces the internal cellresistance, thus enhancing the power capability of electrochemical cell.

In accordance with the present disclosure, a process for synthesis of acomposite material by oxidative polymerization is described. The processincludes contacting SVO with an acidic solution to form a solutioncontaining SVO. The process further includes contacting pyrrole with thesolution containing SVO to form a composite material which includes PPyand SVO.

In certain embodiments, SVQ can be prepared by using a combinationreaction of Ag₂O and V₂O₅ to form an SVO powder. However, other suitablemethods to form SVO can also be utilized including decompositionreactions if so desired.

The acidic solution utilized to contact the SVO can be selected fromvarious acid solutions as would be known to one of skill in the art. Incertain embodiments of the present disclosure, HClO₄ solution can beutilized as the acidic solution.

In some embodiments, after the SVO is contacted with an acidic solution,the solution containing SVO is contacted with nitrogen gas or similarlysuitable material. In some embodiments, such a gas is bubbled throughthe solution for a period of time.

As stated previously, the process further includes contacting pyrrolewith the solution containing SVO to form a composite material whichincludes PPy and SVO. In certain embodiments, various concentrations ofpyrrole can be injected into the SVO containing solution. In someembodiments, liquid pyrrole (98%, Aldrich) can be utilized. However,suitable pyrrole as would be known to one skilled in the art can beutilized as well.

In some embodiments, the pyrrole is injected into the SVO solutionduring vigorous magnetic stirring. However, other suitable methods ofagitating the solution may also be employed.

The process of the present disclosure can optionally include filteringthe polypyrrole and silver vanadium composite material and rinsing anddrying the same. In such embodiments, the composite powders can becollected by filtration and rinsed first with a 1 M HClO₄ solution andthen with deionized water, followed by drying under vacuum or othersuitable drying method.

In accordance with one embodiment of the present disclosure, a compositeelectrode for a battery is provided. Such an electrode can be createdutilizing the process described herein. The electrode includes silvervanadium oxide and polypyrrole.

A suitable carbon material may also be utilized in forming theelectrode. Carbon black is a carbon typical of those used for electrodesin batteries. However, other carbon-containing materials can be utilizedas would be known in the art including but not limited to activatedcarbon and carbon nanotubes.

The silver vanadium oxide can be present in an amount from about 75weight percent to about 99 weight percent. The polypyrrole can bepresent in an amount from about 1 weight percent to about 25 weightpercent.

In certain embodiments, the polypyrrole is present in an amount fromabout 5 weight percent to about 15 weight percent. In some embodiments,the polypyrrole is present in an amount from about 7 weight percent toabout 12 weight percent.

The electrode of the present disclosure can be located in a lithiumbattery such as a lithium primary battery. However, the electrode mayalso be utilized in other types of batteries as would be known to one ofordinary skill in the art.

A battery with an electrode contemplated by the present disclosure canhave a discharge capacity from about 255 mAh g-1 to about 315 mAh g-1.In certain embodiments, the battery can have a discharge capacity fromabout 275 mAh g-1 to about 310 mAh g-1. In certain embodiments, thebattery can have a discharge capacity from about 285 mAh g-1 to about305 mAh g-1.

The electrode of the present disclosure can be can be utilized as acathode in a lithium/silver vanadium oxide primary battery. Such abattery could be utilized for various applications, including medicaldevices. In such medical devices, accurate prediction of the lifetime ofthe battery is of importance, and the electrode of the presentdisclosure is advantageous in that regard. Suitable medical devicesinclude implantable cardio-verter defibrillators or other devices inwhich a battery containing an electrode of the present disclosure wouldbe of benefit

The following examples are provided to illustrate the present inventionand is not intended to limit the scope of the invention.

EXAMPLES

Preparation of PPy/SVO Composites

SVO was prepared by using a combination reaction of Ag₂O and V₂O₅. Amixture of Ag₂O (99+%, Alfa Aesar) and V₂O₅ (99.995%, Alfa Aesar) in 1:2molar ratio was heat-treated in either N₂ or air at 520° C. for 24 h.As-heat-treated sample with a dark brown color was then pulverized bygrinding into fine powders. The SVO powder specimens synthesized in N₂and air are denoted as SVO(N) and SVO(A), respectively.

The composite specimens of PPy and SVO were chemically synthesized by anoxidative polymerization of pyrrole monomer on the SVO surface asfollows: the SVO(A) powders prepared in an air atmosphere were dispersedin a 1 M HClO₄ solution, followed by bubbling with N₂ for 30 minutes.Various concentrations of liquid pyrrole (98%, Aldrich) were then slowlyinjected into the SVO(A)-containing solution during vigorous magneticstirring. The resulting PPy/SVO(A) composite powders with a black colorwere collected by filtration and were thoroughly rinsed first with a 1 MHClO₄ solution and then with deionized water, followed by drying undervacuum at 80° C. for 12 hours.

Materials Characterizations

In order to identify the crystal structures of the synthesized powderspecimens, X-ray diffraction (XRD) patterns were recorded with anautomated Rigalu diffractometer using Cu K_(α) radiation over thescanning angle range of 10 to 60° at the scan rate of 4° min⁻¹. Fouriertransform-infrared (FT-IR) spectra were performed on pellets by using aNicolet 4700 FT-IR spectrometer under transmittance mode.Thermogravimetric analysis (TGA) was conducted to determine the PPycontent in composite using a Perkin-Elmer TGA7 thermogravimetricanalyzer. The powder specimens were heated in a helium flow from roomtemperature to 500° C. at the scan rate of 5° C. min⁻¹.

Electrochemical Experiments

The active material powders were mixed with 5 wt % carbon black(acetylene, 99.9%, Alfa Aesar) and 5 wt % polytetrafluoroethylene (PTFE,Aldrich) to prepare a pellet with a diameter of 1 cm. A three-electrodeelectrochemical cell was employed for the electrochemical experiments.Both the reference and counter electrodes were constructed from lithiumfoil (electrochemical grade, FMC Corporation), and 1 M LiPF₆-DME/PC(50:50 vol %, Ferro Corporation) was used as the electrolyte. Theassembly of cells was performed in a glove box filled with purifiedargon gas.

Galvanostatic discharge experiments were carried out with an ArbinBT-2043 battery test station at various current densities with thecut-off potential being 1.5 V vs. Li/Li⁺. Chronoamperometric techniqueand electrochemical impedance spectroscopy (EIS) were performed using anEG&G PAR model 273 potentiostat combined with a Solartron 1255 frequencyresponse analyzer. Chronoamperometric and impedance measurements wererun by applying a potential drop of 25 mV and by applying anac-amplitude of 5 mV peak-to-peak over the frequency range from 10 mHzto 100 kHz, respectively.

Characterizations of PPy/SVO Composite Electrodes

FIG. 1 (a)-(c) present powder XRD patterns of pristine SVO(N), SVO(A)and PPy/SVO(A) composite, respectively. When compared with the XRDpattern for SVO(A), the pattern for SVO(N) shows two additional peaks atabout 22.6° and 25.1° both of which are attributed to thenon-stoichiometric Ag_(1.2)V₃O₈ phase. On the basis of a ternary phasediagram for Ag₂O—V₂O₅—V₂O₄, the appearance of Ag_(1.2)V₃O₈ phase inSVO(N) can be explained by a ‘sprouting phenomenon’ which refers to thephase transformation of Ag₂V₄O_(11-y) to Ag_(1.2)V₃O₈ duringheat-treatment in an inert atmosphere.

Since the extra electrons of the double bond in a conjugated system arefree to move through the polymer chain, PPy is an inherent conductingpolymer. However, in order to have a high electrical conductivity itshould exist in the oxidized form. During the polymerization process,the SVO(A) surface should be negatively charged to compensate thepositive charges developed on the oxidized form of PPy. Thus, it isexpected that the formation of V⁴⁺ species on the SVO(A) surfaceaccompanies the oxidative polymerization of pyrrole monomer in an acidicHClO₄ solution. Since the XRD pattern of PPy/SVO(A) composite is exactlythe same as that of pristine SVO(A), the results indicate that a smallamount of V⁴⁺ species does not induce any significant structuralmodification of SVO(A) during the polymerization process.

FIGS. 2 (a) and (b) show the FT-IR spectra obtained for the KBr-dilutedpellets of pristine SVO(A) and PPy/SVO(A) composite, respectively. Inboth spectra, the characteristic absorption bands of the V—O—V and V═Ovibrations are observed at approximately 750 and 925 cm⁻¹, respectively.In addition, the FT-IR spectrum of PPy/SVO(A) composite exhibits twoabsorption bands around 1050 and 1190 cm⁻¹ which can be assigned to theN—H and C—H in-plane vibrations in PPy, respectively. This resultconfirms that SVO can be successfully used as an oxidizing agent topolymerize pyrrole monomer on its surface in an acidic HClO₄ solution,leading to the PPy/SVO composite electrode.

The PPy content in the PPy/SVO(A) composite electrode was determined byestimating the weight loss of the composite material during atemperature scan carried out from room temperature to 500° C. in ahelium flow. The PPy was found to completely decompose at approximately420° C., which agrees well with our previous finding onPPy/Co_(0.2)CrO_(x) composites. FIG. 3 shows the amounts of PPy andSVO(A) in the composite electrode as a function of the liquid pyrroleconcentration injected into the polymerization bath. As theconcentration of pyrrole monomer increases to 0.2 M, the PPy contentgradually increases up to 20.2 wt %. The composite electrodes with 0-15wt % PPy were subjected to extensive electrochemical characterizationstudies.

Electrochemical Performances of PPy/SVO Composite Electrodes

FIGS. 4 (a) and (b) present the galvanostatic discharge curves obtainedat C/25 rate and the discharge capacity vs. rate dependence,respectively. The discharge curves were recorded on three types ofelectrodes: pristine SVO(N), SVO(A) and 7 wt % PPy/SVO(A) compositeelectrode. The value of the specific discharge capacity was calculatedbased on the weight of the active material rather than the weight ofpellet with conductive carbon and organic binder.

The results presented in FIGS. 4 (a) and (b) indicate that threedistinct potential plateaus are observed at 2.8, 2.5 and 2.1 V vs.Li/Li⁺. The observed plateaus correspond to the reduction reactions of(i) Ag⁺ to Ag, (ii) V⁵⁺ to V⁴⁺ (and V⁴⁺ to V³⁺) and (iii) V⁴⁺ to V³⁺,respectively. The discharge capacity determined at the cut-off potentialof 1.5 V vs. Li/Li⁺ increases in the order of pristine SVO(N), SVO(A)and PPy/SVO(A) composite. Since only four moles of lithium can beelectrochemically intercalated into Ag_(1.2)V₃O₈, a lower dischargecapacity of the pristine SVO(N) electrode we believe is attributable tothe presence of Ag_(1.2)V₃O₈ phase which is confirmed by the XRD patternin FIG. 1 (a). The PPy/SVO(A) composite electrode shows the highestdischarge capacity of ca. 297 mAh g⁻¹. As shown in FIG. 4 (a), thesecond potential plateau of PPy/SVO(A) composite is larger when comparedto that of pristine SVO(A), which indicates that PPy contributes mainlyto an increase in the discharge capacity of the composite electrode atapproximately 2.5 V vs. Li/Li⁺. It is also of importance to note thatthe improvement in the discharge capacity of PPy/SVO(A) composite asshown in FIG. 4 (b) remains over a wide range of discharge rates,indicating an enhanced rate capability of the composite material.

FIG. 5 (a) presents the discharge capacities of the PPy/SVO(A) compositeelectrodes which contain various PPy contents. For comparison, thetheoretical dependence of the discharge capacity on the PPy content isalso presented in FIG. 5 (a). Besides the fact that bare PPy is known tobe electrochemically active for lithium intercalation, it typically hasmuch lower capacity of ca. 72 mAh g⁻¹ than the bare SVO, and hence thetheoretical discharge capacity of PPy/SVO(A) composite should decreaselinearly with increasing PPy content. However, the galvanostaticdischarge data in FIG. 5 (a) clearly show that the discharge capacity ofPPy reaches a maximum for PPy content between about 7.0 and 12.5 wt %.

The composite electrode yields higher discharge capacity than thepristine SVO(A) electrode. In case of PPy/SVO(A) composite, the synergicelectrochemical performance exceeds the sum of PPy and SVO(A)'sindividual performances indicating that besides the fact that PPy iselectrochemically active (it possesses its own capacity to intercalatelithium ions), it also promotes lithium insertion into SVO(A).

FIG. 5 (b) shows the utilization of SVO(A) in the composite electrode asa function of the PPy content. The utilization was calculated from themeasured discharge capacity of PPy/SVO(A) by assuming a full utilizationof PPy with a capacity of 72 mAh g⁻¹. The PPy content in the compositein the range of about 7.0 to 12.5 wt % causes SVO(A) to be fullyutilized during the discharge process,

Kinetic Studies on Lithium Intercalation into PPy/SVO CompositeElectrodes

Chronoamperometry (potentiostatic current transient technique) was usedto estimate the rate-determining steps which control the lithiumintercalation. If lithium intercalation is controlled by diffusionwithin the bulk of the electrode, the relationship between the current Iand time t is given by Cottrell equation:

$\begin{matrix}{{I(t)} \approx {\frac{Q\sqrt{{\overset{\sim}{D}}_{Li}}}{L\sqrt{\pi}}t^{- \frac{1}{2}}\mspace{14mu}{for}\mspace{14mu} t} ⪡ \frac{L^{2}}{{\overset{\sim}{D}}_{Li}}} & (1)\end{matrix}$where Q is the total charge transferred over the whole lithiumintercalation, {tilde over (D)}_(Li) is the chemical diffusivity oflithium while L denotes the diffusion length. According to Eq. (1), theCottrell region is characterized by a plateau in the It^(1/2) vs. log tplot (Cottrell plot). Therefore, the Cottrell plot can provide adiagnostic tool for identifying the intercalation behavior of lithium.

FIG. 6 presents typical chronoamperometric curves obtained for 7 wt %PPy/SVO(A) composite electrode. The experiments were performed byshifting the applied potential from 3.0 to 2.975 V vs. Li/Li⁺ and from2.9 to 2.875 V vs. Li/Li⁺. The corresponding Cottrell plots wereconstructed from the chronoamperometric curves. Since any plateau regionis absent throughout the entire intercalation time, one can conclude anon-diffusion-controlled process of lithium intercalation. Thenon-Cottrell behavior in FIG. 6 suggests that lithium intercalation intothe PPy/SVO(A) composite electrode is not controlled by diffusion alone,but rather it proceeds under the mixed control by the interfacial chargetransfer and diffusion reactions.

In view of the mixed control process, the useful information that helpsto understand the enhanced SVO(A) utilization in the composite electrodecan be acquired by analyzing two kinetic parameters, namely the chargetransfer resistance and the lithium diffusivity.

FIG. 7 (a)-(c) demonstrate typical Nyquist plots of the ac-impedancespectrum obtained for 7 wt % PPy/SVO(A) composite electrode. Theelectrode was polarized at 3.4, 2.8 and 2.0 V vs. Li/Li⁺, respectively.Each of the ac-impedance spectra consists of two separated arcs in thehigh frequency range and a straight line inclined at constant angle tothe real axis in the low frequency range. The magnitude of the first arcis almost independent of the electrode potential, while the second arcshows a strong potential-dependence. Various models have been proposedto explain such a two-arc behavior of the ac-impedance in intercalationcompounds. It is generally accepted that the first arc is mainly causedby the formation of the passive film on the surface of the oxideparticle, and the second arc is ascribed to the interfacial chargetransfer reaction.

A straight line at low frequencies is associated with semi-infinitediffusion of lithium in the electrode (Warburg impedance). The idealdiffusion impedance should exhibit the phase angle of about 45°;however, according to FIG. 7, the absolute value of the phase angle forthe measured diffusion impedance is higher than 45° at 3.4 V vs. Li/Li⁺,and it decreases to values lower than 45° with decreasing electrodepotential. The decreasing tendency of the absolute phase angle withlowering electrode potential has been also observed for V₂O₅. Theanomalous behaviors of diffusion impedance with absolute phase anglesgreater and lower than 45° can be explained in terms of the particlesize (diffusion length) distribution and of the activation energydistribution for diffusion through the electrode, respectively. Theabnormal behaviors of diffusion impedance lie beyond the scope of thiswork.

FIG. 8 compares the plots of the charge transfer resistance for pristineSVO(A) and for 7 wt % PPy/SVO(A) composite as a function of theelectrode potential. The data were obtained by using complex nonlinearleast squares (CNLS) fitting of the ac-impedance spectra. The chargetransfer resistance of PPy/SVO(A) composite decreases drastically whencompared to the pristine SVO(A) over the whole potential range. It isconceivable that an enhanced charge transfer kinetics results from aconductive PPy network on the SVO(A) surface.

Since the measured diffusion impedance deviates from the ideal Warburgbehavior, it is difficult to exactly determine the chemical diffusivityof lithium {tilde over (D)}_(Li) from the ac-impedance spectra. Thevalue of {tilde over (D)}_(Li) was alternatively evaluated from thepotential transient and coulometric titration curve:

$\begin{matrix}{{\overset{\sim}{D}}_{Li} = {{\frac{4}{\pi}{\left( \frac{I_{app}V_{M}}{{FA}_{g}} \right)\left\lbrack \frac{\left( {{\mathbb{d}E}/{\mathbb{d}x}} \right)}{\left( {{\mathbb{d}E}/{\mathbb{d}\sqrt{t}}} \right)}\; \right\rbrack}\mspace{11mu}{for}\mspace{14mu} t} ⪡ \frac{L^{2}}{{\overset{\sim}{D}}_{Li}}}} & (2)\end{matrix}$where I_(app) is the applied current; V_(M) the molar volume of theelectrode; F the Faraday constant; A_(g) the superficial geometric areaof the electrode; E the electrode potential and x means the lithiumcontent in the electrode.

The values of {tilde over (D)}_(Li) for pristine SVO(A) and for 7 wt %PPy/SVO(A) composite are plotted in FIG. 9 as a function of theelectrode potential. The plots presented in FIG. 9 indicate that {tildeover (D)}_(Li) for both tested materials has similar dependence on theapplied electrode potential showing two minima at about 2.6 and 2.9 Vvs. Li/Li⁺.

The results indicate that PPy facilitates the interfacial chargetransfer kinetics by forming an effective conductive network on theSVO(A) surface and improves the utilization of the composite electrode.

Conclusions

Galvanostatic discharge experiments showed that the composite electrodeswith 7.0 to 12.5 wt % PPy yield higher discharge capacity and ratecapability when compared to the pristine SVO electrode. The utilizationstudies indicate that PPy facilitates the interfacial charge transferand improves the utilization of the composite electrode.Chronoamperometric measurements indicate that lithium intercalation issimultaneously controlled by the interfacial charge transfer anddiffusion reactions. The analyses of the ac-impedance spectra and thepotential transients indicate that the charge transfer resistance isreduced by addition of PPy, while the lithium diffusivity remains nearlyconstant, regardless of the presence and absence of PPy. Thus, nosignificant influence of PPy on the diffusion kinetics of lithium wasobserved.

These and other modifications and variations to the present disclosurecan be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present disclosure, which ismore particularly set forth in the appended claims. In addition, itshould be understood that aspects of the various embodiments can beinterchanged both in whole or in part. Furthermore, those of ordinaryskill in the art will appreciate that the foregoing description is byway of example only and is not intended to limit the disclosure sofurther described in such appended claims.

What is claimed:
 1. A process for synthesis of a composite electrode ina battery comprising: contacting silver vanadium oxide with an acidicsolution to form a solution containing silver vanadium oxide; contactingpyrrole with said solution containing silver vanadium oxide to form acomposite material comprising polypyrrole and silver vanadium oxide;forming a composite electrode in a battery, wherein said compositeelectrode comprises said composite material; and wherein said batteryhas a discharge capacity from about 255 mAh g⁻¹ to about 315 mAh g⁻¹. 2.The process of claim 1, further comprising contacting said solutioncontaining silver vanadium oxide with N₂ prior to contacting saidsolution containing silver vanadium oxide with said pyrrole.
 3. Theprocess of claim 1, further comprising filtering said polypyrrole andsilver vanadium composite material.
 4. The process of claim 3, furthercomprising rinsing and drying said polypyrrole and silver vanadiumcomposite material.
 5. The process of claim 1, wherein said polypyrroleis present in an amount from about 1 weight percent to about 25 weightpercent.
 6. The process of claim 1, wherein said polypyrrole is presentin an amount from about 5 weight percent to about 15 weight percent. 7.The process of claim 1, wherein said polypyrrole is present in an amountfrom about 7 weight percent to about 12 weight percent.
 8. The processof claim 1, wherein said acidic solution comprises HCIO₄.
 9. The processof claim 1, further comprising synthesizing said silver vanadium oxidethrough a combination reaction of silver oxide and vanadium pentoxide,wherein said combination reaction comprises heat-treatment in anenvironment comprising air.